Inline Property Initializers and Read-Only Auto-Properties

Properties can now be initialized directly at their declaration, eliminating the need for a constructor. Additionally, getter-only auto-properties can be assigned during initialization.

public class Employee
{
    public int Id { get; set; } = 0;
    public string FullName { get; set; } = "Unknown";
    public DateTime HireDate { get; } = DateTime.Now;
}

String Interpolation

Prepend a string with $ to embed expressions directly in side curly braces. Format specifiers and alignment are supported.

var emp = new Employee { Id = 42, FullName = "Alice" };
string line1 = $"Employee: {emp.FullName}, ID: {emp.Id:D5}";
string line2 = $"Hired on {emp.HireDate:yyyy-MM-dd}";
Console.WriteLine($"{line1}\n{line2}");

Expression-Bodied Members

Methods and read-only properties consisting of a single expression can be written using the => lambda‑style syntax.

public class Person
{
    public DateTime BirthDate { get; set; }

    // Expression-bodied property (read‑only)
    public int Age => DateTime.Today.Year - BirthDate.Year;

    // Expression-bodied method
    public string GetDisplayName(string firstName, string lastName) => $"{lastName}, {firstName}";
}

Indexer‑Style Collection Initialization

Dictionary and other indexable collections can be populated using an indexer syntax within the initializer block, improving readability.

var departments = new Dictionary<int, string>
{
    [1] = "Engineering",
    [2] = "Marketing",
    [3] = "Finance"
};

Static Using Directives

Import a static class with using static and call its methods without the class qualifier, reducing repetitive code.

using static System.Console;

public class Logging
{
    public static void WriteMessage(string text)
    {
        WriteLine($"[INFO] {text}");
    }
    public static int MaxValue(int x, int y) => Math.Max(x, y); // also using Math
}

The nameof Operator

nameof obtains the string name of a variable, type, or member at compile time, avoiding magic strings that break during refactoring.

public class Validator
{
    public static void EnsureNotNegative(int quantity)
    {
        if (quantity < 0)
            throw new ArgumentOutOfRangeException(
                nameof(quantity),
                $"Value must be non‑negative but was {quantity}.");
    }
}

Null‑Conditional Operators

The ?. and ?[] operators return null when the left-hand side is null, avoiding NullReferenceException. Combined with the null‑coalescing operator ??, a fallback value can be provided.

string[] items = { "one", null, "three" };

foreach (var item in items)
{
    int length1 = item?.Length ?? 0;   //0 for null entries
    Console.WriteLine(length1);
}

// Chaining with properties
Employee manager = null;
string name = manager?.FullName ?? "No manager";